In the hours after the final battle at Hogwarts there were a few surprises. Among them the loud confrontation between Lucius and Draco Malfoy, when Draco renounced his relationship with his father and refused to return to the manor with him. This paled in significance, however, to the discovery made by Harriet Potter upon returning to the Shrieking Shack. The pale still corpse of Professor Severus Snape was, in fact, not a corpse. Snape was alive, barely ,with a faint thready pulse, but alive nonetheless. Healers were swiftly summoned and the professor's still form was urgently transported to St. Mungo's. Once there the battle to save his life began in earnest as Harriet related his heroic part in Voldemort's downfall to the wizarding world.
The healers discovered that Snape had created a potion to counteract the effects of Nagini's venom and put his body into a state of near stasis in the event of being bitten. The new potion had saved his life, leaving him with a network of scars around his neck, recognition as a potions genius and an order of Merlin first class.
August that year
In his personal potions laboratory ,deep in the dungeons of Hogwarts, Professor Severus Snape was working on an experimental potion of his own creation. He was looking for a potion to rid him of the the disfiguring scars around his neck, a feat that no existing healing potion was able to perform. His efforts so far had been unsuccessful, but he had a good feeling about this concoction. Then again he had a good feeling about the six before this. He sighed at his own foolishness and carefully stirred the deep blue liquid, watching as the colour deepened with each moment.
When the colour reached a midnight hue he extinguished the flame below the cauldron and reached for a vial full of a thick silver liquid, unstoppering it and carefully measuring three drops into the cauldron. He watched as the silver swirled in the the dark blue potion like the galaxy swirling in space. As the mixture began to bubble energetically and the silver spread throughout there was a tentative knock at his door.
"Enter." he called, not looking up from his work. He knew it would be Draco, even if the wards had not already alerted him. Draco was the only other person in Hogwarts right now who would have had a reason to disturb his peace in the dungeons. Draco was also, while Lucius and Narcissa awaited trial in Azkaban, his ward.
The door opened and Draco shuffled in, none of his usual deportment and poise were visible, but the lines of worry that graced his brow drew Snape's attention.
"Can I help you Mr Malfoy?" he asked as he reached for a stone bowl full of grey powder.
Draco shifted under his gaze and mumbled something unintelligible at the flagstone floor.
"I'm somewhat busy Draco so out with it." he prompted.
"I just needed some advice, Sir." Draco blurted out, tugging at his collar and turning pink in the face. "I don't know how to, I-I mean..." he lapsed into mumbles again.
"I'm hardly the best person to consult in matters of love Mr Malfoy." Snape sneered, holding the bowl of powder ready to sprinkle into the cauldron when the bubbles stopped. "What makes you think my advice would be beneficial to you?"
Silence again and Snape looks up at Draco, irritated. He leaves the silence hanging heavily as he waits for the boy to fill it. Draco just squirms uncomfortably. He returns his attention to the gently bubbling liquid just as Draco blurts out his revelation.
"I fancy Harriet bloody Potter!"
Snape jolts in surprise and the powder spills into the cauldron with a hiss. There is a blinding red flash and a searing pain in Snape's face and then everything goes dark.
Crisp clean sheets below him. The unmistakable scent of bandages and healing salves. The sensation of a bright and airy room. Severus was fairly certain he wasn't in the dungeons any more. He slowly opened his eyes, squinting in the light,and the hospital wing swam into focus. He tried to sit up and felt a wave of pain throughout his body making him groan aloud.
"Glad to see you are back with us Severus, dear boy." Poppy Pomfrey smiled as she bustled over to check his condition. "The Headmistress is just outside waiting to talk to you."
"What happened?" Snape called, as Poppy hurried to let McGonagall in.
"Severus," began McGonagall, with an air of trepidation, "I'm going to be blunt with you here."
He bit back a scathing comment as she drew a breath.
"The potion that exploded has left you with some unforseen side effects, which we as yet cannot seem to reverse, however we have healers working on it."
"What side effects?" he asked, raising a hand to feel his face and neck. Finding the now familiar scars gone his heart began to race, but there was something else different too. His face felt different, skin more supple. He looked at his hands. They were unstained, and...younger looking? "Minerva?"
Her thin lips pressed together forming a line as she handed him a hand mirror.
His jaw fell slack in shock as he looked at what was presumably his face. There were no scars, no lines, no sickly pallor. His face was smooth, young and almost unrecognisable.
"I...my...I'm..." he looked at Minerva, "this is not possible."
"I'm afraid it is Severus, you're about twenty years younger if I'm any judge, and as yet there seems to be no way to revert you to your real age."
"How do you propose I teach students in September when I look like one of them?" he asked in an uncharacteristically shakey voice.
"Don't worry Severus, Slughorn will be taking potions and covering as head of house for Slytherin while we await news of your cure. We already have a teacher lined up to take defence against dark arts. All you need to do is be here so the healers can work with you to find a solution."
"I can't be seen this way by students," he protested, "I will be a laughing stock."
"On the contrary my boy," Minerva smirked, "nobody will be any wiser. We have come up with the perfect solution, Draco will help."
Snape felt a flash of irritation, this whole mess was because of Draco distracting him. His new face must have been much easier to read as Minerva put a steadying hand to his arm.
"Don't be hard on Draco, he raised the alarm after the explosion. He feels guilty enough for distracting you."
So he should, Snape thought, but he said, "So what is this amazing idea then?"